sample.mathml

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE m:math PUBLIC "-//W3C//DTD MathML 2.0//EN" 
    "http://www.w3.org/Math/DTD/mathml2/mathml2.dtd"[
    <!ENTITY % MATHML.prefixed "INCLUDE">
    <!ENTITY % MATHML.prefix "m">]>
<m:math xmlns:m="http://www.w3.org/1998/Math/MathML">
    <m:mrow>
        <m:mfrac>
            <m:mrow>
                <m:mi>x</m:mi>
                <m:mo>&plus;</m:mo>
                <m:msup>
                    <m:mi>y</m:mi>
                    <m:mn>2</m:mn>
                </m:msup>
            </m:mrow>
            <m:mrow>
                <m:mi>k</m:mi>
                <m:mo>&plus;</m:mo>
                <m:mn>1</m:mn>
            </m:mrow>
        </m:mfrac>
    </m:mrow>
    <m:mrow>
        <m:apply>
            <m:power/>
            <m:apply>
                <m:plus/>
                <m:ci>a</m:ci>
                <m:ci>b</m:ci>
            </m:apply>
            <m:cn>2</m:cn>
        </m:apply>
    </m:mrow>
</m:math>